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See detailPolyethylene-layered silicate nanocomposites prepared by the polymerization-filling technique: synthesis and mechanical properties
Alexandre, Michaël ULg; Dubois, Philippe ULg; Sun, Tao et al

in Polymer (2002), 43(8), 2123-2132

Polyethylene-layered silicate nanocomposites were prepared by the in situ intercalative polymerization of ethylene by the so-called polymerization-filling technique and analyzed by transmission electron ... [more ▼]

Polyethylene-layered silicate nanocomposites were prepared by the in situ intercalative polymerization of ethylene by the so-called polymerization-filling technique and analyzed by transmission electron microscopy (TEM), X-ray diffraction analysis (XRD), differential scanning calorimetry, dynamic mechanical analysis and tensile testing. Non-modified montmorillonite and hectorite were first treated by trimethylaluminum-depleted methylaluminoxane before being contacted by a Ti-based constrained geometry catalyst. The nanocomposite was formed by addition and polymerization of ethylene. In the absence of a chain transfer agent, ultra high molecular weight polyethylene was produced. The tensile properties of these nanocomposites were poor and essentially independent of the nature and content of the silicate. Upon hydrogen addition, the molecular weight of the polyethylene was decreased with parallel improvement of the tensile and shear moduli, in relation to the filler content. The exfoliation of the layered silicates was confirmed by XRD analysis and TEM observation. The mechanical kneading of the molten nanocomposites resulted in the partial collapse of the exfoliated structure driven by the thermodynamic stability of the layered filler. [less ▲]

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See detailThe POLYGAL project : optimization of food conservation using a combination of lactates and polyphenols.
Dure, Rémi ULg; Ladeuze, S.; Martin, E. et al

Poster (2009, November)

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See detailLa polygamie devant la Cour d'arbitrage
Carlier, Jean-Yves ULg

in Journal du Juriste (2005), 42(1), 1

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See detailPolygeneration and HVAC
Andre, Philippe ULg; Adam, Ch.; Aparecida Silva, Cl. et al

Conference (2005, April)

Decentralized cogeneration may help in energy conservation if a large enough amount of heat can be actually recovered. This restriction is becoming more and more severe because of the growing ... [more ▼]

Decentralized cogeneration may help in energy conservation if a large enough amount of heat can be actually recovered. This restriction is becoming more and more severe because of the growing effectiveness of modern power plants. Re-conversion of heating into cooling is not competitive with the use of modern vapor compression chillers. It may just help to extend a little the time during which the co-generation plant can be effectively used. A co-generation plant should not be sized above 30% of the maximal heating power in order to stay energy efficient. The results of a long term case study are summarized in the paper. These results show the incidence of the plant over-sizing : in this case, the system is consuming more than a classical solution [less ▲]

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See detailPolyhedral properties for the intersection of two knapsacks
Louveaux, Quentin ULg; Weismantel, Robert

in Mathematical Programming (2008), 113(1), 15-37

We address the question to what extent polyhedral knowledge about individual knapsack constraints suffices or lacks to describe the convex hull of the binary solutions to their intersection. It turns out ... [more ▼]

We address the question to what extent polyhedral knowledge about individual knapsack constraints suffices or lacks to describe the convex hull of the binary solutions to their intersection. It turns out that the sign patterns of the weight vectors are responsible for the types of combinatorial valid inequalities appearing in the description of the convex hull of the intersection. In partic- ular, we introduce the notion of an incomplete set inequality which is based on a combinatorial principle for the intersection of two knapsacks. We outline schemes to compute nontrivial bounds for the strength of such inequalities w.r.t. the intersection of the convex hulls of the initial knapsacks. An extension of the inequalities to the mixed case is also given. This opens up the possibility to use the inequalities in an arbitrary simplex tableau. [less ▲]

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See detailPolyimide foams derived from a high Tg polyimide with grafted poly(α-methylstyrene)
Hedrick, James L; DiPietro, R.; Plummer, C. J. G. et al

in Polymer (1996), 37(23), 5229-5236

A new route to high-Tg, thermally stable polyimide foams has been developed. Foams were prepared by casting microphase-separated graft copolymers comprising a thermally stable main chain, polyimide, and a ... [more ▼]

A new route to high-Tg, thermally stable polyimide foams has been developed. Foams were prepared by casting microphase-separated graft copolymers comprising a thermally stable main chain, polyimide, and a thermally labile graft, poly(α-methylstyrene). The copolymer compositions were designed so that the thermally labile block would be the dispersed phase. This can unzip to its monomer upon heating, and the decomposition product diffuses out of the film, leaving pores embedded in a matrix of the thermally stable component. The copolymers were synthesized through either the poly(amic acid) precursor, followed by chemical cyclodehydration to the imide form, or the poly(amic alkyl ester) precursor followed by thermal imidization. The decomposition of the α-methylstyrene in the block copolymer was studied by thermogravimetric, dynamic mechanical and thermomechanical analyses. Mild decomposition conditions were required to avoid rapid depolymerization of the α-methylstyrene and excessive plasticization of the polyimide matrix. The foams showed pore sizes with diameters ranging from less than 20 nm to over 1 µm, depending upon the synthetic route employed, and the reduction in the mass density was generally consistent with the starting composition. [less ▲]

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See detailPolyimide nanofoams from aliphatic polyester-based copolymers
Hedrick, James L; Carter, K. R.; Richter, R. et al

in Chemistry of Materials (1998), 10(1), 39-49

High-temperature polymeric foams were prepared using compositionally asymmetric microphase-separated block copolymers where the major component is thermally stable and the minor component is thermally ... [more ▼]

High-temperature polymeric foams were prepared using compositionally asymmetric microphase-separated block copolymers where the major component is thermally stable and the minor component is thermally labile. Upon thermal treatment, the dispersed phase undergoes thermolysis leaving pores the size and shape of which are dictated by the initial copolymer morphology. The driving force behind the survey of aliphatic polyesters as possible labile blocks stems from their quantitative degradation into low-boiling, polar degradation products. Poly(lactones), as a general class of materials, degrade by a backbiting process producing, primarily, monomer and cyclic oligomers. A ring-opening synthetic route to poly(lactones) affords oligomers of predictable molecular weight, narrow molecular weight distribution, and controlled end-group functionality. Block copolymers were prepared using monofunctional caprolactone and valerolactone oligomers and a high-Tg polyimide. Microphase separation was observed in all cases, and the lactone blocks did not crystallize. Thermal decomposition of the caprolactone block was accomplished by heating the copolymer to 370 °C for 5 h. Significant density reductions were found with pore sizes in the 60−70 Å range. [less ▲]

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See detailPolyimide nanofoams from caprolactone-based copolymers
Hedrick, James L; Russell, T. P.; Sanchez, M. et al

in Macromolecules (1996), 29(10), 3642-3646

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See detailPolylactide (PLA) designed with desired end-use properties: 1. PLA compositions with low molecular weight ester-like plasticizers and related performances
Murariu, Marius; Da Silva Ferreira, Amalia; Alexandre, Michaël ULg et al

in Polymers for Advanced Technologies (2008), 19(6), 636-646

Polylactide (PLA) is an attractive candidate for replacing petrochemical polymers because it is biodegradable and produced from annually renewable resources. Characterized by high tensile strength ... [more ▼]

Polylactide (PLA) is an attractive candidate for replacing petrochemical polymers because it is biodegradable and produced from annually renewable resources. Characterized by high tensile strength, unfortunately the brittleness and rigidity of PLA limit its applicability. For a great number of applications such as packaging, fibers, films, etc., it is of high interest to formulate new grades with improved flexibility and better impact properties. In this objective, a specific PLA grade (L/D isomer ratio of 96:4, high molecular weight) was melt-mixed with selected plasticizers: bis(2-ethylhexyl) adipate (DOA), glyceryl triacetate (GTA), and tributyl O-acetylcitrate (TBAC). Their effect on the molecular, thermal, and mechanical properties of PLA was investigated for content up to 20wt% plasticizer and the results were correlated with a particular attention to the relationship between property and application. Using the solubility and interaction parameters, a tentative evaluation of the product that could act as the most effective plasticizer for PLA has been performed and the obtained results have been corroborated with the materials physical properties. Excellent mechanical performances were obtained using the plasticizer having the lowest molecular mass (GTA) and the best interaction parameter. In relation to plasticizer amount/nature, the glass transition temperature of PLA (62-C) is decreased by plasticizing by more than 30-C, whereas better impact properties and lower stiffness are measured. The optimal formulations targeted to the final applications are clearly characterized by specific end-use properties: improved crystallization rates (PLA-DOA); high elongation at break and tensile strength (PLA-GTA, PLA-TBAC), medium to high impact properties (PLA-DOA, PLA-GTA) compositions. [less ▲]

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See detailPolylactide (PLA) – A new way of production
Jacobsen, Sven; Degée, Philippe; Fritz, Hans-Gerhard et al

in Polymer Engineering & Science (1999), 39(7), 1311-1319

Poly(lactide) (PLA), a biodegradable aliphatic polyester with excellent properties for different polymer applications, has been used mostly in the biomedical field, mainly because of its high price ... [more ▼]

Poly(lactide) (PLA), a biodegradable aliphatic polyester with excellent properties for different polymer applications, has been used mostly in the biomedical field, mainly because of its high price, resulting from expensive polymerization and purification techniques. Although this polymer can play a major role in future markets for biodegradable polymers, the current high price has to be reduced significantly to at least $4 US/kg. Therefore, this paper aims to partially review the polymerization techniques traditionally used in PLA synthesis and to propose new developments that enable us to produce these polymers by an innovative process for just a portion of the costs traditionally charged, using reactive extrusion techniques in a closely intermeshing co-rotating twin screw extruder. This paper gives an overview of attainable mechanical properties and future markets. [less ▲]

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See detailPolylactide (PLA)-CaSO4 composites toughened with low molecular weight and polymeric ester-like plasticizers and related performances
Murariu, Marius; Da Silva Ferreira, Amalia; Pluta, Miroslaw et al

in European Polymer Journal (2008), 44

Large amounts of stable b-anhydrite II (AII), a specific type of dehydrated gypsum and a by-produc tof lactic acid production process, can be melt-blended with bio-sourced and biodegradable polylactide ... [more ▼]

Large amounts of stable b-anhydrite II (AII), a specific type of dehydrated gypsum and a by-produc tof lactic acid production process, can be melt-blended with bio-sourced and biodegradable polylactide (PLA) to produce economically interesting novel composites with high tensile strength and thermal stability. To enhance their toughness, while preserving an optimal stiffness, selected low molecular weight plasticizers (bis(2-ethylhexyl) adipate and glyceryl triacetate) and polymeric adipates with different molecular weights have been mixed with a specific PLA (L/D isomer ratio of 96/4) and 40 wt% of AII using an internal kneader. Addition of up to 10 wt% plasticizer into these highly filled compositions can trigger a fourfold increase of the impact strength with respect to the compositions without any modifier, cold crystallization properties and a significant decrease of their glass transition temperature. Moreover, these ternary compositions (PLA–AII–plasticizer) are clearly characterized by easier processing, notable thermo-mechanical performances and good filler dispersion. This study represents a new approach in formulating novel melt-processable polyester grades with improved characteristic features using PLA as biodegradable polymer matrix. [less ▲]

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See detailPolylactide implants and bacterial contamination: an animal study
Mainil-Varlet, Pierre; Hauke, Christian; Maquet, Véronique et al

in Journal of Biomedical Materials Research, Part A (2001), 54(3), 335-343

Although bioresorbable aliphatic polyesters derived from lactic acid are now used clinically as sutures, bone-fracture fixation devices and sustained-release drug-delivery systems, very little is known ... [more ▼]

Although bioresorbable aliphatic polyesters derived from lactic acid are now used clinically as sutures, bone-fracture fixation devices and sustained-release drug-delivery systems, very little is known about their behavior in the infected environment. The aim of the present study was to compare the resistance to infection of two polylactide implants with different degradation characteristics, and to evaluate the influence of a bacterial challenge on their mechanical and physicochemical properties. Various quantities of a beta-haemolyzing strain of Staphylococus aureus (V 8189-94) were inoculated into the medullary cavity of rabbit tibiae, and an extruded polylactide rod composed of either P(L)LA (Poly(L-Lactide)) or P(L/DL)LA (Poly(L/DL-Lactide)) was then inserted. Animals were sacrificed four weeks after surgery. The tibiae and implants were removed under sterile conditions and evaluated microbiologically by culturing. The severity of infection was graded according to positive colony-forming units in the bone. The mechanical properties of the retrieved implants were assessed by 4-point bending and shear tests, performed in compliance with the ASTM D790 standard and their physicochemical characteristics also were characterized. P(L)LA and P(L/DL)LA implants were equally resistant to local infection, their mechanical and physicochemical properties being unaffected by bacterial challenge. Hence, once an infection has become established, the release of bactericidal/bacteriostatic by-products during implant degradation does not appear to affect its natural course. The release of bactericidal/bacteriostatic degradation products at the implantation site is unlikely to affect the natural course of an established infection. [less ▲]

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See detailPolylactide macroporous biodegradable foams by solid-liquid and liquid-liquid phase separation
Maquet, V; Schugens, C; Grandfils, Christian ULg et al

Conference (1995, May 22)

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See detailPolylactide Macroporous Biodegradable Implants for Cell Transplantation. Ii. Preparation of Polylactide Foams by Liquid-Liquid Phase Separation
Schugens, C.; Maquet, Véronique; Grandfils, Christian ULg et al

in Journal of Biomedical Materials Research (1996), 30(4), 449-61

Potential of thermally induced phase separation as a porogen technique has been studied in an effort to produce a surgical implant suitable for cell transplantation. Emphasis has been placed on the liquid ... [more ▼]

Potential of thermally induced phase separation as a porogen technique has been studied in an effort to produce a surgical implant suitable for cell transplantation. Emphasis has been placed on the liquid-liquid phase separation of solutions of amorphous poly DL-lactide and semicrystalline poly L-lactide in an 87/13 dioxane/water mixture. The related temperature/composition phase diagrams have been set up by turbidimetry, and the possible occurrence of a gel has been discussed. Freeze-drying of some phase-separated polylactide solutions can produce flexible and tough foams with an isotropic morphology. Interconnected pores of 1-10 microns in diameter are expected to result from the spinodal decomposition of the polylactide solutions with formation of co-continuous phases. Thermodynamics of the polymer/solvent pair has a decisive effect on the final macroporous foams, as shown by the dependence of their porosity, density, porous morphology, and mechanical behavior on molecular weight and crystallinity of polylactide and concentration of the original solutions. On the basis of the foam characteristics, potential of the liquid-liquid phase separation (spinodal decomposition) has been compared with the solid/liquid phase separation (solvent crystallization) as a porogen technique. [less ▲]

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See detailPolylactide microparticles prepared by double emulsion-evaporation 2 : Effect of the poly(lactide-co-glycolide) composition on the stability of the primary and secondary emulsions
Nihant, Nicole; Schugens, Chantal; Grandfils, Christian ULg et al

in Journal of Colloid and Interface Science (1995), 173(1), 55-65

Polylactide and copolymers with glycolide have been used as coating polymers in the microencapsulation technique based on the W1/o/w2 double emulsion-evaporation method. Stability of the primary emulsion ... [more ▼]

Polylactide and copolymers with glycolide have been used as coating polymers in the microencapsulation technique based on the W1/o/w2 double emulsion-evaporation method. Stability of the primary emulsion is of critical importance and clearly predetermines the internal morphology of the microspheres, in agreement with the very fast hardening of the oil phase (CH2Cl2) as soon as the primary emulsion is dispersed in water. When the peptide or' protein to be encapsulated is able to interact with the coating polymer and possibly with the surfactant, the stabilization mechanism of the primary emulsion is very complex. It has been shown that the interaction of BSA (bovine serum albumin) with the polyester is as strong as the glycolide content is high, which results in the formation of a solid film at the w1/o interface and in a high emulsion stability. Addition of a surfactant, such as poloxamer 188, in the oil phase has a deleterious effect on both the emulsion stability and the internal structure of the microspheres. Use of a dye tracer in the internal aqueous phase was not useful in probing the double emulsion stability and the encapsulation efficiency, because of specific interactions between the dye (indigocarmine) and the coating polyester. [less ▲]

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See detailPolylactide Microparticules Prepared by Double Emulsion/Evaporation Technique. I. Effect of Primary Emulsion Stability
Nihant; Schugens, Chantal; Grandfils, Christian ULg et al

in Pharmaceutical Research (1994), 11(10), 1479-1484

The process of microencapsulation of proteins by double emulsion-evaporation in a matrix of polylactide (PLA) can be divided into three successive steps: first, an aqueous solution of the active compound ... [more ▼]

The process of microencapsulation of proteins by double emulsion-evaporation in a matrix of polylactide (PLA) can be divided into three successive steps: first, an aqueous solution of the active compound is emulsified into an organic solution of the hydrophobic coating polymer; second, this primary water-in-oil (w/o) is dispersed in water with formation of a double water-oil-water emulsion (w/o/w), third, the organic solvent is removed with formation of solid microparticles. This paper focuses of the effect of primary emulsion stability on the morphology and properties of polylactide microparticles loaded with bovine serum albumin (BSA) used as model drug. [less ▲]

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See detailPolylactone based Biomedical Materials : Chemistry and Breakthrough Applications
Dubois, Philippe ULg; Barakat, I; Degée, P et al

Poster (1992, November 22)

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See detailPolymer (PE) synthesis - scaling up to industrial scale
Detrembleur, Christophe ULg

Conference (2007, September 30)

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See detailPolymer based intraocular lens adsorbome: a bottom up proteomics study
Bertrand, Virginie ULg; Huang, Yi-Shiang ULg; Mazzucchelli, Gabriel ULg et al

Conference (2013, September 08)

In the present work an optimized sample preparation protocol to identify and quantify the “adsorbomes” of hydrophilic and hydrophobic materials for IOLs known to have a higher or a lower incidence of PCO ... [more ▼]

In the present work an optimized sample preparation protocol to identify and quantify the “adsorbomes” of hydrophilic and hydrophobic materials for IOLs known to have a higher or a lower incidence of PCO, respectively was obtained. [less ▲]

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See detailPolymer blending: a convenient technique for the preparation of new antimicrobial polymeric mateirals
Lenoir, Sandrine; Pagnoulle, Christophe; Petru, Stiube et al

Poster (2003, May 16)

Detailed reference viewed: 7 (2 ULg)